[shuss]

First off, you're right that readv(), like read() can indeed return lesser data than was requested. Thanks. I'll fix that.

> I'm also actually not sure if in the uring version requests are guaranteed to be processed in order or not. I would have assumed the latter - and thereby the printed result could have been out of order.

io_uring may not make completions available in the same order as submissions. The article goes into some detail explaining this. However, the "cat" example only deals with one request at a time which uses readv() and readv()'s iovecs are returned in order. So, this is not a problem. The "cp" example does deal with multiple submissions and completions, however it uses writev() on the completion of each readv(), writing the correct offsets. So, it wouldn't matter if completions arrive out of order. But this is indeed something to look out for.